At first, rescuers thought that there was just a buildup of fluid in Pip's brain, which was causing blindness in the tiny puppy. But as the swelling went down, rescuers gave the puppy an MRI and found something shocking.

"An MRI scan revealed that she is missing part of her brain which means her optic nerves are not developed and she cannot see," Amy De-Keyzer, RSPCA press officer, told The Dodo. "It's something the neurology team at The Animal Health Trust had never seen before in a dog."

Pip will need lifelong medication, eye drops and regular checkups.

"One theory is that she's been bred from two merle dogs to produce a merle coloring - something which is desirable in today's 'designer dog' culture," De-Keyzer explained. "Breeding from two merles is not recommended as this colored dog can carry a faulty gene and any offspring can be plagued with health problems - like Pip."

"Peggy is missing the lower part of her left rear leg - an injury which has now healed - and we believe she will need considerable veterinary and surgical treatment," Kathy Butler, trustee and dog coordinator with the RSPCA, said in a press release. "The vet believes it is the result of a traumatic injury or could have been caused deliberately. Although amputation is an option, she may be referred for specialist treatment and could be suitable for a prosthetic limb."

Thankfully, the worst could be over for the little family.

"They're safe in our care now and are settling into their foster home," Butler said.

The dogs will need extensive surgery to make a full recovery, according to the RSPCA. Click here to learn how you can help.

The RSPCA is also asking for information to find out who abandoned Peggy and Pip. Anyone with information should contact the RSPCA.

If you'd like to adopt a dog of your own, you can check out Adopt-a-Pet.com to get started.